💉 Polio Vaccine Trials You’ve Never Been Shown Aaron Siri breaks down the licensing data for today’s polio vaccine, IPOL. It was licensed in 1990, and in its clinical trial, safety was only reviewed for three days after injection. THREE. DAYS. There was no control group. This is not the Salk or Sabin vaccine most people think of. This version uses Vero cells, monkey kidney cells modified to replicate indefinitely. Del notes that although some claim the original IPV was tested against a saline p